We will conduct an epidemiologic study (a case-control study) to define the "relative risk" of developing end-stage interstitial nephritis as a consequence of the ingestion of analgesics. The study will involve the gathering of information on all patients currently on dialysis from the greater Phila. region of Eastern Pennsylvania. From this group of patients we will select those whose primary disease is interstitial nephritis. The analgesic ingestion history of this subgroup will be compared to that of controls who are matched for age, sex, and race but have no renal disease. The study will allow us to estimate: 1) the significance if any of the associations between the ingestion of analgesics and the development of end-stage interstitial nephritis; 2) if particular analgesics or combinations of analgesics produce a higher risk than others; 3) if dosgae levels or duration of use influence the development of end-stage interstitial nephritis; 4) the attributable and relative risks of developing analgesic abuse nephropathy. If this study reveals that the association between the use of analgesics and the devlopment of end-stage renal disease is significant, a prospective study designed to determine the exact danger of analgesic use will be implemented.